Amplifier Bias Circuit Preheating for Distortion-Free Startup
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Solution Overview
Problem
Amplifiers experience signal distortion due to temperature non-equilibrium at startup, leading to increased time to reach a stable state and higher circuit complexity to address this issue.
Innovation Solution
An amplification control circuit with a first bias unit generating a preheat control signal based on operational voltage changes and a second bias unit adjusting current output to an output-stage amplifier accordingly, ensuring preheating during the initial operational voltage change period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the amplifier operates immediately at startup, then the amplifier can start working quickly, but the output signal will be distorted due to temperature non-equilibrium
Solution Approach 1:
The patent applies preliminary action by introducing a preheat control signal that activates the output-stage amplifier before the input-stage amplifier fully operates. This preheating phase allows the output-stage amplifier to reach thermal equilibrium in advance, ensuring stable operation and undistorted signal output from the moment the amplifier starts working, thus resolving the contradiction between quick startup and signal quality.
2Reliability
If the amplifier is preheated to reach thermal equilibrium faster, then signal distortion is reduced, but the circuit area and complexity increase
Solution Approach 1:
The patent merges the preheat control function into the existing bias control circuitry. The preheat control signal is generated by the same control unit that manages the bias currents for both input-stage and output-stage amplifiers. This integration allows the preheating function to be added without requiring separate dedicated preheating circuits, thus reducing circuit area and complexity while still achieving thermal equilibrium and eliminating signal distortion.
3Speed
If a larger bias current is applied to the output-stage amplifier, then the amplifier reaches thermal equilibrium faster, but more energy is consumed
Solution Approach 1:
The patent applies periodic action by controlling the bias current to the output-stage amplifier in two distinct phases: a preheat phase with higher current to rapidly reach thermal equilibrium, and a normal operation phase with reduced current for sustained stable operation. The preheat control signal activates the output-stage amplifier with elevated bias current only during the initial startup period, then transitions to standard bias current levels, thus achieving fast thermal equilibrium while minimizing overall energy consumption during normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows the output-stage amplifier to reach thermal equilibrium faster, reducing signal distortion and minimizing circuit complexity by eliminating the need for repeated preheating circuits.
Implementation Method 1
generate a preheat control signal according to a change of the operational voltage signal
Implementation Method 2
The second current in a first period is larger than the second current in a second period, the first period starts from a beginning of the change of the operational voltage signal
Implementation Method 3
allows the output-stage amplifier to reach thermal equilibrium faster
Data Source
AI summary
An amplifier control circuit includes a first bias unit and a second bias unit. The first bias unit outputs a first current to a first amplifier. The first bias unit includes a primary bias circuit and a preheat signal generation circuit. The primary bias circuit receives an operational voltage signal, outputs the first current and outputs a detection signal. Change of the operational voltage signal is related to change of the detection signal. The preheat signal generation circuit generates a preheat control signal according to the change of the detection signal. The second bias circuit outputs a second current to a second amplifier. The second current in a first period is larger than the second current in a second period. The first period starts after the operational voltage signal starts to change, and the second period starts after the first period ends.